Step down xfmr to connect a 480 V inverter to 208Y120 system

[Giark]

What are the issues to consider when connecting an inverter with an output of 480 V to a 208y120 service through an xfmr? I can see it working as a step down xfmr from the inverters point of view. But it is also a reverse fed xfmr part of the time.

 

[jaggedben]

You seem to be asking if there are any fundamental issues with having a transformer work in two directions. The answer to that is no, a single transformer will function in either direction.

If you have an more specific question, I'll leave that up to the experts, of which I am not one on this subject.

 

[tallgirl]

I'm with jaggedben -- there is no issue with the transformer going one way rather than the other.

The only issue I can think of is insertion losses due to the transformers, and the associated costs for the transformer(s). Where's the nearest 480 volt connection? Cheaper than a transformer to get there?

 

[GoldDigger]

I'm with jaggedben -- there is no issue with the transformer going one way rather than the other.

The only issue I can think of is insertion losses due to the transformers, and the associated costs for the transformer(s). Where's the nearest 480 volt connection? Cheaper than a transformer to get there?

The only things that I can see as significant are details related to the insertion loss:

If you want to run a transformer at full output in the "forward" direction, the turn ratio of primary to secondary may be offset from the voltage ratio number to produce the desired secondary voltage from a nominal primary voltage.
That same offset to the turn ratio will act in the wrong direction when the transformer is used in reverse.
But for connecting a grid tie PV inverter, the inverter will operate over a wide enough range of voltages that this should not be a factor. Instead just the power loss enters into the calculation.
And the magnetizing current for the core may be added to the nominal current for the "secondary" winding rather than the "primary" winding when calculating the power dissipated in the windings.